Neuraxial Opioids and Postcesarean Hypoxemia
Abstract Number: F-19
Abstract Type: Original Research
Introduction: Obstetric anesthesiologists administer intrathecal or epidural opioids for postcesarean analgesia, but late respiratory depression may occur 8-10 hours after administration due to rostral spread in the cerebrospinal fluid (CSF).
Methods: In a retrospective study of consecutive cesarean deliveries in a 3 month period at the University of Missouri, the incidences of hypoxemia and need for supplemental oxygen in the first 20 hours postpartum was studied. Patient charts were reviewed for patient comorbidities, neuraxial opioid administration parameters (choice of opioids, time of administration, intrathecal or epidural site), and additional medications, vital signs, oxygen saturations, and oxygen therapy administered.
Results: All patients were initially divided into three groups: ITM = intrathecal morphine 0.2 mg (with or without intrathecal fentanyl 20 mcg) [n = 83]; EPM = epidural morphine 4 mg [n = 46]; and EMB = epidural morphine 4 mg plus butorphanol 3 mg [n = 12]. All documented respiratory rates were 18 breaths per minute or greater. Outcomes for oxygen administration and degree of oxygen desaturation are presented in tables 1 and 2. Statistical analysis used Fisher’s Exact test.
The choice of initial opioid(s) (including dose and route of opioid administration), alone, did not differ significantly in contributing to depressed respiratory rates, oxygen desaturation, or need for supplemental oxygen. Because the most critical desaturations occurred in patients with systemic diseases (asthma, morbid obesity, CVA) who received additional opioids (morphine, meperidine, fentanyl) and rescue medications with sedative properties (diphenhydramine, promethazine), we plan to do a multifactorial weighted comparison of all contributing factors.
Discussion: Risk factors for postcesarean hypoxemia in our patient population included morbid obesity, asthma, CNS disease, receiving additional opioids, sedatives, and tranquilizers, especially in combination, during normal sleeping hours, and with inappropriately high reported patient pain scores. Future studies will examine the relative risk of each of these contributing factors. Since roughly one quarter of our patients had one or more of these conditions and desaturated to 94% or below, continuous pulse oximetry monitoring and liberal prescribing of supplemental oxygen is recommended.